How do I build up the endurance to do a 8 mile commute on my bicycle?

[Frieza C]

Its downhill mostly up there but uphill going back. I weigh 270 pounds. How do I build up the endurance to do a 8 mile commute up there and back?

 

[Jeffery]

set goals and bike alot often. in the spring i could barely bike up this 600ft hill near my house, now i do it easily but i also average 30km a day... so just keep pushing yourself to ride further and do the rides to where your biking to faster and faster.